Blast furnace backdraft valve



May 6, 1969 H, A R ET' AL 3,442,484

BLAST FURNACE BACKDRAFT VALVE 7 Filed Aug. 29, 1966 Sheet' of 2 Cover in full open position NVENTORS. HUGH 8. CARR and ELMER W. TUROCY A r I orneys Sheet 4 of 2 y 6, 1969 H. B. CARR ET AL BLAST FURNACE BACKDRAFT VALVE Filed Aug. 29. 1966 mm km wn 9 mm an R an kw 3 9 3 mm \w E Q E 3 T E 9 9w 9 I. Q m 9 E mm m I LI INVENTORS. HUGH B. CARR and ELMER W. TUROCY Alrarneys United States Patent US. Cl. 251-98 4 Claims ABSTRACT OF THE DISCLOSURE A backdraft valve is disclosed which is adapted to be used in a system where there is a pressure against the valve when it is closed. The valve includes a valve body having a valve seat ring at the top thereof and a cap-like valve member adapted to seat on the seat ring when the valve is closed. A lever is pivotally secured to the valve body, and the valve member is hung from the free end of the lever. Latch means are provided for holding the valve member seated on the seating ring and a common operating mechanism is provided to first release the latch means when it is desired to open the valve and then rock the lever to lift the valve member off the seat and move it to a position at one side of the valve body, and when it is desired to close the valve to first move the valve member to seating position and then move the latch means into latching engagement with the valve member.

This invention is for a valve of the cap type designed to be used at the top of a stack and seat against the top of the stack on which it is mounted, and especially on a stack which may be normally subjected to pressure of high temperature gases.

The valve is especially designed for use on a stack employed in a blast furnace plant to divert backdraft of gases and air to the atmosphere when, for any reason, the blast is shut down. It may be explained that in a blast furnace plant there are generally at least three stoves which are used more or less in rotation to heat air for delivery to the blast furnace. Air is blown through one stove at a time and discharged from the stove into the hot blast main through which it flows under pressure to the bustle pipe of the blast furnace from which it is then conducted through tuyeres into the bosh of the furnace. When, for any reason, this blast is shut down, there is a backdraft causing gases and air in the furnace to flow in the reverse direction through the hot blast main into one or more of the stoves and eventually be discharged to atmosphere.

This backdraft is now considered to be detrimental to the stoves, so that it has been proposed to insert a disk type valve, known in the art as a hot blast valve, in the hot blast main between the bustle pipe and the stoves which may be closed to prevent the backdraft into the stoves. This requires a stack to be put in the hot blast main between said valve and the bustle pipe of the furnace to vent the backdraft gases. However, under normal conditions of operation, this stack must be closed to prevent the hot blast air intended for the furnace blowing out through the stack, and because of the high temperatures encountered, and to conserve heat, this stack must be refractory lined.

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For a number of reasons that need not be all explained here, it is both most economical and desirable to pro vide this valve at the top of the stack. One reason is that the refractory is protected from alternate exposure to high temperature and then the ambient temperature of the atmosphere, such alternate heating and cooling being conducive to spalling and destruction of the refractory.

The present invention provides a cap type of valve adapted to seat on a ring at the top of the valve body with a latch for holding it tightly closed when hot air under pressure is flowing through the hot gas main, together with an operatin mechanism that releases the latch and then effects opening of the valve when backdraft gases are to be vented, and which again latches the valve in closed position after the valve has been restored to that position.

The invention further provides a novel valve and seating ring arrangement to assure effective sealing of the valve when it is closed and latched.

The invention may be more fully understood by reference to the accompanying drawings showing an embodiment of our invention and wherein:

FIG. 1 is a side elevation of the valve and its operating mechanism;

FIG. 2 is an elevation at right angles to FIG. 1;

FIG. 3 is a top plan view of the mechanism shown in FIG. 1; and

FIG. 4 is a fragmentary detail showing a portion of the valve and its seat in transverse vertical section.

In the drawings, wherein like reference numerals designate like parts throughout, 2 designates a cylindrical valve body formed of metal and lined with refractory to form in effect a continuation of the vertical stack on top of which it is mounted, the body 2 having a flange 3 at its base by means of which it may be bolted to a flange at the top of the stack indicated in broken lines at 4.

Surrounding the body near the top thereof is a laterally-extending flange 5 which is best seen in FIG. 4, which serves to support a tightly fitted annular seating ring 6 that is replaceable, and which is held in place on the flange 5 by bolts 7. This seating ring has a beveled top surface 8 that slopes downwardlyand inwardly toward the center of the valve body, its inner edge desirably being just about flush with the top of the refractory lining '9. The seat is preferably made of a special alloy steel.

The valve which is in the form of a cap designed to cover the top end of the body when it is in closed position is designated generally as 10 and it comprises a metal shell 11 with a refractory lining 12, the inner face of the metal cap 11 being concaved to receive the refractory. The down-turned peripheral edge 13 of the metal shell is beveled to seat squarely on the beveled surface 8 of the seating ring 6 when the valve is in closed position.

The valve 10 has an upstanding ear or lug .14 thereon at the center thereof, and this lug extends between parallel bars 15 which, together, form the operating lever for the valve. A bolt 16 passes through the arms 15 and the lug 14 for pivotally suspending the valve 10 at its center from the operating lever. The operating lever 15 comprising two parallel bars has two cross arms thereon providing four lateral extensions 17, each of which has an adjusting bolt 18 at its outer end. One cross arm is forward of the pivot 16, that is near the free end of the lever, and the other is to the rear of the pivot. Each bolt 18 is positioned above a pad 19 on the top of the valve, the pivoted suspension for the valve enabling it to conform to the seat which it engages while the bolts 18 act to level the valve and limit its hinging movement relative to the arm 15.

The lever 15 comprised of the two bars is essentially one arm of a bell crank which is pivotally supported on a pivot pin 20 passing through the lever and passing through a supporting lug structure 21 welded to the upper portion of the valve body. Lever 15, which is horizontal when the valve is closed, has the end which is pivoted bent downwardly, there being a vertical reach 15' so that the pivotal support 20 for the lever 15 is below the seating ring 6. The bell crank lever has a second horizontallyextending lever arm 15a which is shorter than the valvecarrying lever 15.

There is a pivot pin 22 at the outer end of the arm 15a that passes through an elongated opening or slot 23 at the top of an operating link 24 so that there may be relative movement between the link 24 and the outer end of the arm 15a of the lever assembly 15. The extent of this relative lost motion may be adjusted by means of an adjusting screw 25 at the top end of the link 24, the screw projecting down into the opening or slot 23 in the path of movement of the pin 22.

The lower end of the link 24 is pivotally connected at 25a. to an operating crank 26 that is keyed to a transverse shaft 27 carried on brackets 28 secured to the body of the valve near its lower end.

Projecting laterally from each side of the valve are latching lugs 30. At diametrically opposite sides of the valve body near the top there is a hook-like latch element 31 having an end portion 32 that normally overhangs the lug 30. The lever is in a plane midway between these latch members. Latch element 31 is mounted on a trunnion 33 supported in a bracket 34 welded to the side of the body 2 near the top thereof, but below the seat. The latch member 31 is in the form of a bell crank having a horizontally-extending arm 35. Pivotally attached to the arm 35 at 36 is one end of a link 37. The link 37 has an adjusting nut 38 similar to a turnbuckle by means of which its length may be adjusted, and there is a lock nut 39 to hold it in adjusted position. The lower end of the link 38 has a curved extension 40 which is pivotally connected at 41 o a lever 42 also keyed to the rock shaft 27. The latchoperating assembly above described is the Same on each side of the valve body.

The shaft 27 may be rotated through a limited are by any suitable means. There is here shown for this purpose a reducing gear 43 of the type having a hand wheel 44 by which it may be turned, or which may be operated by an electric motor 45. Drives of this kind usually embody a worm gear (not shown) that engages a worm wheel (not shown) within a housing 46, this worm wheel being keyed to the shaft 27.

Since the valve is generally located at the top of a stack where the hand wheel is inaccessible, the hand wheel is of a sprocket type. An operating chain 48 passes around the hand wheel and also through guides 49, so that the hand wheel may be turned from a position on the ground or well below the top of the stack.

When the valve is closed the cap valve member 10 is tightly seated on the seating ring 6, as shown in FIG. 4, and the parts are in full line position best shown in FIG. 1. When the back draft valve is to be opened, the operating mechanism 43 is operated to rotate the shaft 27 in a counterclockwise direction as viewed in FIG. 1. The counterclockwise movement of the crank or arm 42 on the shaft 27 exerts tension on the link 37, pulling down on the latch arm 35 to move the tip 32 of the latch 31 clear of the lug 30, the latch elements 31 rocking on their respective trunnions 33. It will be understood that this operation occurs simultaneously at both sides of the valve body because of the duplication of the latch and latch-operating mechanism at each side of the valve body. During this movement of the latch to the released position the link 24 is being pulled down by the crank 26, but because of the lost motion provided through the opening of slot 23 at the upper end of the link 24 no motion is transmitted initially to the valve 10. However, when the latch is free of the lug 30, continued rotation of the shaft 27 then causes the arm 15a of the lever 15 to be pulled down, rocking the lever 15 about its pivot 20, lifting valve 10 free of the top of the valve body and moving it to a vertical or near vertical position clear of the top of the valve body, as partially indicated in broken lines in FIG. 1. During this opening of the valve the pin 22 at the outer end of arm 15a is in contact with the adjusting screw 25 at the top of the link 24.

When the valve is to be closed, the shaft 27 is rotated in the reverse direction and the valve 10 is brought to position over the top of the valve body and lowered, the pivoting suspension of the valve on the arm 15 allowing it to adjust itself to the valve seat while the leveling bolts 18 aid in effecting proper seating of the valve. As soon as the valve is seated it can move no further. However, the weight of the cap valve as it swings to a horizontal position holds the pivot 22 in contact with adjusting screw 25 until the valve is seated. Then the link 24 moves up relatively to arm 15a to operate the latches to latching position.

As thus constructed the valve in closed position is latched against the seat and held down to resist a pressure of several pounds per square inch, thereby resisting the pressure of the hot blast air in the stack from raising the valve 10. However, when the valve is to be opened the leverage effects the unlatching of the valve before it is raised, and the mechanism assures that the valve will be again raised when it is next closed.

The valve and operating mechanism are relatively inexpensive, and once in position with the proper adjustment of the link 37 and the lost motion adjustment 25, proper sequence of movement of the valve and latching and unlatching is established. Since the cap valve swings in an are from the closed to the open position about a pivot point 20 located out from the side of the stack, there is no hinging of the edge 13 of the valve on the seat 8, and therefore there is little wear. However, if it becomes necessary, the seat ring 6 may be readily replaced.

We claim:

1. A backdraft valve of the type to be used in a system where there is pressure against the valve when it is closed, comprising a body adapted to be secured to the top of a stack, a valve seat ring at the top of the body, a caplike valve member adapted to seat on the seat ring when the valve is closed, a lever secured to the valve body and extending over the valve member and from the free end of which the valve member is hung, latch means movable into and out of latching engagement and latching the valve member on its seat when the valve member is seated, and a common operating mechanism comprising a rock shaft having a crank a-rm thereon operatively connected with the lever through a lost motion linkage and having a second crank arm thereon operatively connected with the latch means through a linkage, the operating mechanism arranged to first release the latch means when it is desired to open the valve and then rock said lever to lift the valve member off the seat ring and move it to a generally vertical position at one side of the body and when it is desired to close the valve to first move the valve member to a seating position and then move the latch means into latching engagement with the valve member.

2. A backdraft valve as defined in claim 1 in which the latch means comprises a pair of latching elements, each one of the latching elements being pivotally supported on the body at diametrically-opposite sides thereof, said lever being in a position between the two latching elements, the valve member having a pair of latching lugs projecting from the periphery thereof at each side of the lever, the latching elements each having a portion that projects over one of said lugs when the valve is latched shut, said second crank arm transmitting a pivotal movement to said latch elements when said rock shaft is rotated.

3. A backd'raft valve as defined in claim 1 in which the valve member is pivotally hung with the pivot being above the center of the valve member, said lever having cross arms thereon forwardly and rearwardly of the center, and an adjusting screw at each end of each cross arm for contacting the top of the valve member and limiting its pivotal movement.

4. A 'backdraft valve as defined in claim 1 in which the valve seat tightly encircles the top of the valve body but is separated therefrom.

References Cited UNITED STATES PATENTS 1,783,621 12/1930 Johnson 251147 5 2,235,308 3/1941 Banker 25178 2,596,805 5/1952 Banker 251147 2,868,496 1/1959 Decker 251147 3,037,737 6/1962 Konemund et al. 251299 10 M. CARY NELSON, Primary Examiner.

W. R. CLINE, Assistant Examiner.

US. Cl. X.R. 251147 

